Machine shop work often require the fabrication of a replacement part for a worn out machine or other equipment that is broken down for example. Because it is often difficult to bring the equipment to the shop, dimensions for the new part are often taken in the field. For this type of machine shop jobs for example, there is a need for a measuring instrument which can be used to obtain the measurement between bolt holes on a part to be replaced without having to take the part off the machine at that time.
The prior art contains several trammel-like instruments for taking distance between holes. The following documents provide a good inventory of the measuring devices available from the prior art:    U.S. Pat. No. 893,562 issued to H. B. Ash on Jul. 14, 1908;    U.S. Pat. No. 1,166,512 issued to F. M. Dannenfelser on Jan. 4, 1916;    U.S. Pat. No. 1,422,345 issued to W. Douglas on Jul. 11, 1922;    U.S. Pat. No. 2,419,752 issued to G. F. Zumbuhl on Apr. 29, 1947;    U.S. Pat. No. 2,463,796 issued to C. J. O'Rourke on Mar. 8, 1949;    U.S. Pat. No. 2,532,376 issued to R. Smith on Dec. 5, 1950;    U.S. Pat. No. 2,537,473 issued to R. W. McCusker on Jan. 9, 1951;    U.S. Pat. No. 2,539,097 issued to C. J. O'Rouke on Jan. 23, 1951;    U.S. Pat. No. 2,645,022 issued to J. M. Hart on Jul. 14, 1953;    U.S. Pat. No. 2,693,033 issued to H. W. Acker Jr. et al. on Nov. 2, 1954;    U.S. Pat. No. 2,821,027 issued to J. J. Billhimer, Sr. on Jan. 28, 1958;    U.S. Pat. No. 2,830,378 issued to D. E. Givan on Apr. 15, 1958;    U.S. Pat. No. 2,941,303 issued to F. J. Middlestadt on Jun. 21, 1960;    U.S. Pat. No. 2,974,416 issued to P. G. Zurcher on Mar. 14, 1961;    U.S. Pat. No. 3,289,307 issued to E. J. Kelly on Dec. 6, 1966;    U.S. Pat. No. 3,483,631 issued to R. Bourgeois on Dec. 16, 1969;    U.S. Pat. No. 3,522,658 issued to J. F. Howell on Aug. 4, 1970;    U.S. Pat. No. 3,672,064 issued to J. C. Elkins et al. on Jun. 27, 1972;    U.S. Pat. No. 3,816,933 issued to R. R. Dillinger on Jun. 18, 1974;    U.S. Pat. No. Des 245,967 issued to G. N. Chartier on Oct. 4, 1977;    U.S. Pat. No. 4,327,493 issued to L. R. Dickerson on May 4, 1982;    U.S. Pat. No. 4,353,169 issued to E. M. Mitchell on Oct. 12, 1982;    U.S. Pat. No. 4,547,973 issued to F. L. Owens on Oct. 22, 1985;    U.S. Pat. No. 4,730,399 issued to R. Campbell on Mar. 15, 1988;    U.S. Pat. No. 5,509,208 issued to C. J. Oja on Apr. 23, 1996;    U.S. Pat. No. 5,807,036 issued to Tad. K. Lostlen on Sep. 15, 1998;
The apparatus of the prior art identified above are usable for taking measurements along a straight line or in orthogonal directions only. These devices cannot be used to obtain the position of holes in an asymmetric array for example.